Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 19: Poster: Interfaces and Thin Films
CPP 19.22: Poster
Dienstag, 15. März 2011, 18:00–20:00, P2
The mesoscopic structure of liquid–vapour interfaces — •Felix Höfling and Siegfried Dietrich — Max-Planck-Institut für Metallforschung, Heisenbergstraße 3, 70569 Stuttgart, and Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart
The interfacial region between coexisting phases, e.g., between liquid and vapour, is broadened and roughened by thermal fluctuations. The spectrum of these fluctuations diverges for large wavelengths according to the phenomenological capillary wave theory (CWT). Deviations from CWT have been predicted by density functional theory for inhomogeneous fluids [1]. In particular, an enhancement of fluctuations at mesoscopic wavenumbers is expected due to the long-ranged nature of the intermolecular dispersion forces.
We have performed extensive molecular dynamics simulations for a simple liquid of up to one million particles interacting via a truncated Lennard–Jones potential. Macroscopic properties such as the interface width and the surface tension have been determined and their dependence on system size and cutoff radius of the potential is discussed. Further, the interface structure as encoded in the position-dependent density-density correlation function H(z1, z2, k) is analysed. A factorisation property is tested on the obtained data and the wavenumber-dependent surface tension is extracted. Finally, we will address consequences of an external gravitational field on the interface structure.
[1] K. Mecke and S. Dietrich, Phys. Rev. E 59, 6766 (1999).